Difference between Cause & effect and Control Narratives

[mrkssastry]

A good start for the explanation. I just want to add the following.

1. Control Narrative: It is a document which explains the functioning of DCS system - control loops, open loops, duty / standby pump operations, duty, standby, assist operations, etc. For a control loop, the control narrative document explains the type of control (PID / PI / P / ratio control / cascade control / feedforward control etc), control set point, controller action, output direction, modes of operation of the controller (manual mode, auto mode, cascade mode etc), PV tracking options, output type in case of controller failure (output goes to 100% / 0%, stay put / stay safe) etc.


For a duty standby pump operation the control narrative explains the concept of auto changeover in detail - wht happens when there is a trip of first pump, what should happen to the system when the cmmand goes to pump for start but it does not start etc. It also explains under what circumstances auto changeover is achieved and under what circumstances, operator intervention is required.

2. Cause & Effect chart: The name itself is very clear. It clearly is a document which explains if a cause happens what should be the effect. Typically C&E charts are prepared for ESD, F&G, all the individual package systems where PLC systems are involved in implementing interlocks. DCS system is not an exception to this. Even DCS system can have its own C&E even though there is a separate ESD system to take care of the shutdown.

Hope i am clear. Please do not hesitate to ask more in case of clarification.

[josefreitas]

In my project we need to do a SIL study. The Client specify SIL 3 for Control. You can help me with a SIL report in order to check the process phases that i need to analyse. I appreciate if can send to me one report jose_manuel_freitas@yahoo.com